Cased telescoped ammunition is under consideration for use in ground vehicle, ship and aircraft mounted guns. The projectile is completely enclosed, or telescoped, within the cartridge case and surrounded by consolidated propellant, therefore reducing the volume required for a gun, ammunition storage and feed mechanism or gun system using such ammunition by a significant amount compared with equivalent gun systems using conventionally shaped rounds. The cartridge case of cased telescoped ammunition allows for a simpler, more reliable and more compact gun system with a higher rate of fire.
In cased telescoped ammunition, the projectile is accelerated initially by a booster charge to close, or to obturate, the barrel of the gun before the main propellant charge is fully ignited and to mitigate the peak chamber pressure. A control tube or core tube has been employed in the past to control the initial movement of the projectile. A booster charge may be located in the control tube and is separated by the tube from the main propelling charge. The booster charge is placed aft of the projectile. Main charge ignition does not occur until the advancing projectile clears the tube or exposes or unblocks ignition ports in the wall of the control tube which permits products of the burning booster charge to ignite the main charge. Ignition of the main charge is controlled by the position of the projectile. Main propellant ignition occurs when the projectile is at a known and reproducible location in the round and has moved toward the barrel of the gun from which it is being fired. There should be minimal venting, blow-by, or pressure leakage of the gases produced by the ignited propellant as the projectile accelerates down the gun barrel. An example of a cased telescoped round is disclosed in U.S. Pat. No. 4,858,533 to Warren, which is hereby incorporated by reference, and teaches a cased telescope ammunition round with a full caliber core tube each end of which is respectively connected to the front and rear seals of the cylindrical casing of the round with a fin stabilized penetrator and its sabot positioned within the control tube prior to firing.
U.S. Pat. No. 5,063,852 to Warren, which is hereby incorporated by reference, teaches a cased telescoped ammunition round for a fin stabilized penetrator projectile. The cylindrical casing has a rear seal closing the rear end of the casing and a front seal secured to the front end of the casing. A tapered full caliber control tube is secured to the front seal of the casing. The thickness of the side walls of the control tube increases, or the side walls are tapered, from the rear end to the forward end.
U.S. Pat. No. 5,042,388 to Warren et al., which is hereby incorporated by reference, teaches a cased telescoped ammunition with a perforated forward control tube, in which the main propellant gas and flame front ignites the propellant surrounding the tube through the control tube perforations after the obturator passes the perforations. Seals form annular segments of consolidated propellant surrounding the tube separated from each other and the main propellant charge. These seals limit the ignition path of the propellant surrounding the tube to the control tube perforations or ports which have been passed by the obturator.
The dimensions of the casing of cased telescoped ammunition rounds fired by a given type gun system are fixed. The dimensions of the projectile are determined and therefore, the space available for the propellant and other necessary parts is limited. To maximize the performance of a projectile there is a need to maximize the amount of propellant contained within each round by increasing the space available for propellant without reducing the reliability of the gun system while maintaining consistent performance of each round as fired.
Further, it is advantageous to reduce the weight of the round for ease of use by eliminating unnecessary parts of the ammunition but while maintaining high performance achieved with a sequenced ignition. The elimination of parts also leads to a reduction in cost of the round and simplification of the round leads to a better performing round of ammunition.